1. Field of the Invention
The present invention relates to a gas-supplying apparatus for a fuel cell and a particularly to a gas-supplying apparatus for a fuel cell, which can decrease electric power consumption and which can make it easy to discharge the produced water to drive the fuel cell in an adequate manner.
2. Description of Related Arts
A fuel cell (proton exchange membrane type fuel cell) has recently drawn considerable attention as a power source of an electric powered vehicle because of its cleanness and excellent energy efficiency. Into the fuel cell, fuel gas (hydrogen) and oxidant gas (air) are supplied to electrochemically generates power.
As a gas-supplying apparatus for a fuel cell, which supplies gas to the fuel cell, an apparatus having an air compressor whose motive source is electric power generated by the fuel cell which is provided on the upstream of the fuel cell, and which compressively transfers supply air into the fuel cell has been utilized. For example, Japanese Patent Laid-Open Publication No. 8-167422 discloses a fuel cell having an air supplying system (gas-supplying apparatus for a fuel cell) in which an air compressor is provided on the upstream of the fuel cell and a pressure control valve is provided on the downstream of the fuel cell.
While the fuel cell produces water due to an electrochemical reaction, the produced water, if it stays within the fuel cell, inhibits the power generation. For this reason, in the conventional fuel cell system, supply air is compressively transferred from the air compressor in the gas-supplying apparatus for a fuel cell provided on the upstream of the fuel cell, whereby the produced air is entrained with the supply air to be discharged.
However, the gas-supplying apparatus for a fuel cell in which the supply air is compressively transferred has the disadvantage in terms of a large amount of pressure loss, which consumes wasteful electric power (parasitic power of the fuel cell) as a motive force of the air compressor. The motive power for the motor includes the electric power generated by the fuel cell. The produced water is produced in a large amount, when an airflow amount is large, in which case the electrochemical reaction is strongly brought about in the fuel cell. On the other hand, when an airflow amount becomes large, pressure loss also becomes large accordingly. For this reason, a large amount of the motive force (electric power) is required for discharging the produced water, which leads to the problem that the produced water can be discharged only with difficulty.